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The regulation of miRNA-211 expression and its role in melanoma cell invasiveness.

Mazar J, DeYoung K, Khaitan D, Meister E, Almodovar A, Goydos J, Ray A, Perera RJ - PLoS ONE (2010)

Bottom Line: KCNMA1 mRNA and protein expression levels varied inversely with miR-211 levels.The transcription factor MITF, important for melanocyte development and function, is needed for high TRPM1 expression.MITF is also needed for miR-211 expression, suggesting that the tumor-suppressor activities of MITF and/or TRPM1 may at least partially be due to miR-211's negative post transcriptional effects on the KCNMA1 transcript.

View Article: PubMed Central - PubMed

Affiliation: Sanford Burnham Medical Research Institute, Orlando, Florida, United States of America.

ABSTRACT
The immediate molecular mechanisms behind invasive melanoma are poorly understood. Recent studies implicate microRNAs (miRNAs) as important agents in melanoma and other cancers. To investigate the role of miRNAs in melanoma, we subjected human melanoma cell lines to miRNA expression profiling, and report a range of variations in several miRNAs. Specifically, compared with expression levels in melanocytes, levels of miR-211 were consistently reduced in all eight non-pigmented melanoma cell lines we examined; they were also reduced in 21 out of 30 distinct melanoma samples from patients, classified as primary in situ, regional metastatic, distant metastatic, and nodal metastatic. The levels of several predicted target mRNAs of miR-211 were reduced in melanoma cell lines that ectopically expressed miR-211. In vivo target cleavage assays confirmed one such target mRNA encoded by KCNMA1. Mutating the miR-211 binding site seed sequences at the KCNMA1 3'-UTR abolished target cleavage. KCNMA1 mRNA and protein expression levels varied inversely with miR-211 levels. Two different melanoma cell lines ectopically expressing miR-211 exhibited significant growth inhibition and reduced invasiveness compared with the respective parental melanoma cell lines. An shRNA against KCNMA1 mRNA also demonstrated similar effects on melanoma cells. miR-211 is encoded within the sixth intron of TRPM1, a candidate suppressor of melanoma metastasis. The transcription factor MITF, important for melanocyte development and function, is needed for high TRPM1 expression. MITF is also needed for miR-211 expression, suggesting that the tumor-suppressor activities of MITF and/or TRPM1 may at least partially be due to miR-211's negative post transcriptional effects on the KCNMA1 transcript. Given previous reports of high KCNMA1 levels in metastasizing melanoma, prostate cancer and glioma, our findings that miR-211 is a direct posttranscriptional regulator of KCNMA1 expression as well as the dependence of this miRNA's expression on MITF activity, establishes miR-211 as an important regulatory agent in human melanoma.

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A model summarizing the regulation and role of miR-211 in melanoma.MITF, a transcription factor with tumor-suppressor activity, is active in melanocytes, where it is required for the expression of TRPM1, the structural gene for melatonin-1. miR-211 gene is located within the sixth intron of TRPM1, which is co-transcribed with the TRPM1 transcript, is processed to active miR-211 and subsequently the latter acts on the 3′-UTR of KCNMA1 transcript. We propose that inhibition of KCNMA1 translation is needed for preventing the development of invasive melanoma. MITF activity is low in melanoma cells, which is expected to reduce TRPM1 as well as miR-211 transcription, therefore would induce the expression of KCNMA1. While it is widely held on the basis of expression pattern alone that TRPM1 is a putative tumor suppressor, we show that miR-211, contained within the pre-mRNA of TRPM1 transcript, also has a tumor suppressor activity through its negative regulation on KCNMA1.
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pone-0013779-g009: A model summarizing the regulation and role of miR-211 in melanoma.MITF, a transcription factor with tumor-suppressor activity, is active in melanocytes, where it is required for the expression of TRPM1, the structural gene for melatonin-1. miR-211 gene is located within the sixth intron of TRPM1, which is co-transcribed with the TRPM1 transcript, is processed to active miR-211 and subsequently the latter acts on the 3′-UTR of KCNMA1 transcript. We propose that inhibition of KCNMA1 translation is needed for preventing the development of invasive melanoma. MITF activity is low in melanoma cells, which is expected to reduce TRPM1 as well as miR-211 transcription, therefore would induce the expression of KCNMA1. While it is widely held on the basis of expression pattern alone that TRPM1 is a putative tumor suppressor, we show that miR-211, contained within the pre-mRNA of TRPM1 transcript, also has a tumor suppressor activity through its negative regulation on KCNMA1.

Mentions: The TRPM1 gene, which contains miR-211 sequences in the sixth intron, was previously suggested to be a suppressor of melanoma aggressiveness [61], [62]. We showed here that the transcription factor MITF, which regulates the expression of TRPM1, is also needed for high-level expression of miR-211. Thus, the regulation by MITF of both TRPM1 and miR-211 genes can be speculated to have similar effects on melanoma invasiveness separately through their respective gene products: the former a Ca++ channel protein (TRPM1), and the latter a miRNA targeted against the Ca++ regulated K+ channel protein KCNMA1. If true, the invasiveness of melanoma cells could partly be the result of the breakdown of processes related to calcium-regulated ion homeostasis. The recent finding that salinomycin, an inhibitor of K+ transport, is a selective inhibitor of cancer stem cell proliferation is consistent with our findings on the role of KCNMA1 in melanoma cells [63]. We cannot eliminate the formal possibility that the potential tumor suppressor activity of TRPM1 gene is, at least in part, due to the co-expression of miR-211 encoded from within its sixth intron. In Figure 9 we summarize our results, in light of previous studies, as a simple model of the mechanism of development of invasive melanoma, which highlights the role of miR-211.


The regulation of miRNA-211 expression and its role in melanoma cell invasiveness.

Mazar J, DeYoung K, Khaitan D, Meister E, Almodovar A, Goydos J, Ray A, Perera RJ - PLoS ONE (2010)

A model summarizing the regulation and role of miR-211 in melanoma.MITF, a transcription factor with tumor-suppressor activity, is active in melanocytes, where it is required for the expression of TRPM1, the structural gene for melatonin-1. miR-211 gene is located within the sixth intron of TRPM1, which is co-transcribed with the TRPM1 transcript, is processed to active miR-211 and subsequently the latter acts on the 3′-UTR of KCNMA1 transcript. We propose that inhibition of KCNMA1 translation is needed for preventing the development of invasive melanoma. MITF activity is low in melanoma cells, which is expected to reduce TRPM1 as well as miR-211 transcription, therefore would induce the expression of KCNMA1. While it is widely held on the basis of expression pattern alone that TRPM1 is a putative tumor suppressor, we show that miR-211, contained within the pre-mRNA of TRPM1 transcript, also has a tumor suppressor activity through its negative regulation on KCNMA1.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2967468&req=5

pone-0013779-g009: A model summarizing the regulation and role of miR-211 in melanoma.MITF, a transcription factor with tumor-suppressor activity, is active in melanocytes, where it is required for the expression of TRPM1, the structural gene for melatonin-1. miR-211 gene is located within the sixth intron of TRPM1, which is co-transcribed with the TRPM1 transcript, is processed to active miR-211 and subsequently the latter acts on the 3′-UTR of KCNMA1 transcript. We propose that inhibition of KCNMA1 translation is needed for preventing the development of invasive melanoma. MITF activity is low in melanoma cells, which is expected to reduce TRPM1 as well as miR-211 transcription, therefore would induce the expression of KCNMA1. While it is widely held on the basis of expression pattern alone that TRPM1 is a putative tumor suppressor, we show that miR-211, contained within the pre-mRNA of TRPM1 transcript, also has a tumor suppressor activity through its negative regulation on KCNMA1.
Mentions: The TRPM1 gene, which contains miR-211 sequences in the sixth intron, was previously suggested to be a suppressor of melanoma aggressiveness [61], [62]. We showed here that the transcription factor MITF, which regulates the expression of TRPM1, is also needed for high-level expression of miR-211. Thus, the regulation by MITF of both TRPM1 and miR-211 genes can be speculated to have similar effects on melanoma invasiveness separately through their respective gene products: the former a Ca++ channel protein (TRPM1), and the latter a miRNA targeted against the Ca++ regulated K+ channel protein KCNMA1. If true, the invasiveness of melanoma cells could partly be the result of the breakdown of processes related to calcium-regulated ion homeostasis. The recent finding that salinomycin, an inhibitor of K+ transport, is a selective inhibitor of cancer stem cell proliferation is consistent with our findings on the role of KCNMA1 in melanoma cells [63]. We cannot eliminate the formal possibility that the potential tumor suppressor activity of TRPM1 gene is, at least in part, due to the co-expression of miR-211 encoded from within its sixth intron. In Figure 9 we summarize our results, in light of previous studies, as a simple model of the mechanism of development of invasive melanoma, which highlights the role of miR-211.

Bottom Line: KCNMA1 mRNA and protein expression levels varied inversely with miR-211 levels.The transcription factor MITF, important for melanocyte development and function, is needed for high TRPM1 expression.MITF is also needed for miR-211 expression, suggesting that the tumor-suppressor activities of MITF and/or TRPM1 may at least partially be due to miR-211's negative post transcriptional effects on the KCNMA1 transcript.

View Article: PubMed Central - PubMed

Affiliation: Sanford Burnham Medical Research Institute, Orlando, Florida, United States of America.

ABSTRACT
The immediate molecular mechanisms behind invasive melanoma are poorly understood. Recent studies implicate microRNAs (miRNAs) as important agents in melanoma and other cancers. To investigate the role of miRNAs in melanoma, we subjected human melanoma cell lines to miRNA expression profiling, and report a range of variations in several miRNAs. Specifically, compared with expression levels in melanocytes, levels of miR-211 were consistently reduced in all eight non-pigmented melanoma cell lines we examined; they were also reduced in 21 out of 30 distinct melanoma samples from patients, classified as primary in situ, regional metastatic, distant metastatic, and nodal metastatic. The levels of several predicted target mRNAs of miR-211 were reduced in melanoma cell lines that ectopically expressed miR-211. In vivo target cleavage assays confirmed one such target mRNA encoded by KCNMA1. Mutating the miR-211 binding site seed sequences at the KCNMA1 3'-UTR abolished target cleavage. KCNMA1 mRNA and protein expression levels varied inversely with miR-211 levels. Two different melanoma cell lines ectopically expressing miR-211 exhibited significant growth inhibition and reduced invasiveness compared with the respective parental melanoma cell lines. An shRNA against KCNMA1 mRNA also demonstrated similar effects on melanoma cells. miR-211 is encoded within the sixth intron of TRPM1, a candidate suppressor of melanoma metastasis. The transcription factor MITF, important for melanocyte development and function, is needed for high TRPM1 expression. MITF is also needed for miR-211 expression, suggesting that the tumor-suppressor activities of MITF and/or TRPM1 may at least partially be due to miR-211's negative post transcriptional effects on the KCNMA1 transcript. Given previous reports of high KCNMA1 levels in metastasizing melanoma, prostate cancer and glioma, our findings that miR-211 is a direct posttranscriptional regulator of KCNMA1 expression as well as the dependence of this miRNA's expression on MITF activity, establishes miR-211 as an important regulatory agent in human melanoma.

Show MeSH
Related in: MedlinePlus